Pulse generator



Feb. 24, 1948. DQE'. NORGAARD 2,436,662.

PULSE GENERATOR Filed se t. 2, 1944 PULSE GENERATOR UTILIZATION APPARATUS Fig.2

B C '23 K U7 Inventor 7 Donald ENoTTgaard',

- His Attofney;

Patented Feb. 24, 1948 PULSE GENERATOR Donald E. Norgaard, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application September 2, 1944, Serial No. 552,419

6 Claims. (01. 178-44) My invention relates to electrical pulse generators and particularly to high frequency generators for producing pulses of predetermined fixed duration at preselected times. This application is a continuation-in-part of my copending application Serial No. 482,403, filed April 9, 1943, for Pulse systems, and assigned to the same assignee as the present application.

In the pulse system described in my aforesaid copending application a generator is provided for producing a pulse having a duration of one microsecond and occurring at the end of a period of time preselected within a period of from one to five microseconds. My present application relates to this type of generator and it is an object of my invention to provide an improved generator for producing voltage pulses of precise duration at a preselected time.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompan ing drawing in which Fig. 1 represents a pulse generator embodying my invention and Fig. 2 represents certain operating characteristics of the generator of Fig. 1.

The generator illustrated in Fig. 1 includes an apparatus I of any suitable type for producing, for example, a square pulse of voltage, as indicated at A, which may have any duration within a predetermined range which may be selected by movement of a selector arm 2 associated with the apparatus I. The voltage pulse A is impressed on a control electrode 3 of an electron discharge device 4 through a suitable coupling capacitor 5 and across a resistor 5. The electron discharge device 4 includes a cathode l and an anode 8; a resistor 9 is provided in series with the cathode bypassed by a capacitor H3 to provide a negative bias for the control electrode 3 and to render the device A normally nonconducting. The voltage pulse A is impressed on the grid 3 in a positive sense and the device 4 is rendered conducting, a corresponding pulse of current flowing through a resistor ll connected between the anode B and a suitablesource of direct current potential indicated as a battery I2. In the present instance it may be assumed that the pulse A has been selected to have a duration of approximately two microseconds and, further, the desired pulse may be assumed to be a square pulse of one microsecond duration which occurs at a period after the initiation of the pulse A equal to the duration of the pulse A, the time of cocurrence of the desired one microsecond pulse being selected by varying the length of the pulse A by operation of the selector arm 2. In order to produce a pulse having a duration of one microsecond, I provide an artificial transmission line I3 shunting the resistance II and comprising a series of inductances I4 and shunt capacities I5 and which is short circuited at its remote end IS. The constants of the line I3 are so proportioned that one-half microsecond is required for a voltage variation to travel from the resistance II to the remote end I6 of the line and, therefore, one microsecond is required before any reflection of the voltage variation from the shortcircuited end It appears at the resistance II. The resistance I I is selected to have a value equal to the characteristic impedance of the transmission line so that when the reflected pulse returns to the input end of the line the voltage on the resistance I I disappears because the current flowing through the resistance is effectively neutralized by the reflected current flowing from the line and no further reflections occur. This first onemicrosecond pulse is a negative voltage pulse and although it is impressed on a control electrode ll of an electron discharge device I8 through a I capacitor I9 and across a resistance 26, it has no effect on the operation of the device I8 because this device is biased beyond cutoff by a suitable cathode resistor 2 I. The flow of current through the device 4 ceases immediately upon the termination of the pulse A and a second voltage pulse appears across the resistance 5 I and is terminated in one microsecond upon its reflection from the short-circuited end I6. This pulse is a square pulse and in a positive sense, as indicated at 22 on the curve B in Fig. 2, the initial negative pulse being indicated at 23. The positive pulse 22 evercomes the bias on the control electrode H and renders the device I8 conducting, and, thereupon, current flows between the cathode 25 and the anode 25 of the device iii. The pulse 2'2 is thereby amplified and appears as a pulse 25 at the anode 25, as indicated in the curve C of Fig. 2. Thus the pulse 26 is of one microsecond duration and occurs at the end'of the period determined by the duration of the pulse A. The pulse 26 is supplied to suitable utilization apparatus 2'! which, for example, may be the transient generator disclosed in my aforesaid copending application. v 7

From a consideration of the foregoing description it will be evident that the sudden change in the negative direction at the end of the pulse A determines the time at which the positive pulse 22 begins. It will, therefore, be apparent that pulses other than square pulses may be employed provided they have an abrupt termination. For example, apositive sawtooth wave of predetermined duration might be impressed on the control grid 3 in order to obtain 'a positive pulse of the desired duration when the sawtooth wave is terminated. While the line [3 has been described above as providing a pulse of one microsecond,

this value has been given only by way of illustration, it being understood that'the length of' the line is to be determined in accordance with the desired duration of the signal pulse to be produced at the output of the apparatus.

It is readily apparent from the foregoing that I have provided a simple and effective generator circuit for producing a pulse of high frequency energy having a predetermined precise duration and at a preselected time with a predetermined period of time. When I have shown a particular embodiment of my invention other arrangements will readily occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the particular arrangement illustrated, and I intend in the appended claims to cover all modifications which fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A generator for producing a pulse of predetermined duration at a preselected time comprising first and second electron discharge devices each having an anode and a cathode and a control electrode, means for producing an abruptly terminated wave of selectively variable duration greater than the duration of the desired pulse and for impressing said wave on the pedance element connected between the anode and cathode of said first device, and means incontrol electrode of said first device, an im-' eluding a transmission line connected to the control electrode of said second device and having its input terminals connected across said impedance element for producing a pulse of predetermined duration at the termination of said Wave.

2. A generator for producing a square pulse of predetermined duration at the end of a preselected period of time comprising means for producing a square wave of selectively variable duration greater than the duration of the desired square pulse, an impedance element, means for impressing said square wave on said element, and means including a transmission line having its input terminals connected across said element for producing square pulses of equal predetermined duration but of opposite sense respectively at the beginnin and at the end of said square wave,

3. A generator for producing a square pulse of predetermined duration at the end of a we selected period of time comprising" means for producing a square wave of selectively variable duration greater than the duration of the desired square pulse, a resistor, means for impressing said square wave on said resistor, and means including a transmission line connected to said resistor for producing square pulses of equal predetermined duration but of opposite sense respectively at the beginning and at the end of said square wave, said transmission line having a characteristic impedance equal to the impedance of said resistor and having its terminals at one end connected across said resistor and its terminals at the other end short circuited whereby the duration of said square pulse is equal to twice the delay time of said transmission line.

4. A generator for producing a square pulse of predetermined duration at the end of a preselected period of time comprising first and second electron discharge devices each having an anode and a cathode and a control electrode, means for producing a square wave of selectively variable duration greater than the duration of the desired square pulse and for impressing said wave on the control electrode oi said first device, an impedance element, and means including a transmission line connected to the control electrode of said second device and having its input terminals connected across said element for producing square pulses of equal predetermined duration but of opposite sense respectively at the beginning and end of said square wave.

5. A generator for producing a square pulse of predetermined duration at the end of a preselected period of time comprising first and second electron discharge devices each having an anode and a cathode and a control electrode, means for producing a square wave of selectively variable duration greater than the duration of the desired square pulse and for impressing said wave on the control electrode of said first device to amplify said wave, means coupling the anode of said first device and the control electrode of said second device, a resistor connected between the anode and the cathode of said first device, and a transmission line short circuited at one end and having its terminals at the other end con nected across said resistor for producing square pulses of equal predetermined duration but of opposite sense respectively at the beginning and at the end of the amplified square wave at the anode of said first device.

6. A generator for producing a square pulse of predetermined duration at the end of a preselected period of time comprising first and second electron discharge devices each having an anode and a cathode and a control electrode, means biasing said devices to be normally nonconducting, means for producing a square wave of selectively Variable duration greater than the duration of the desired square pulse and for impressing said wave 'in a positive sense on the control electrode of said first device to amplify said Wave, means coupling the anode of said first device and the control electrode of said second device, a resistor connected between the anode and cathode of said first device, and a transmission line short circuited at one end and having terminals at the other end connected across said resistor for producing square pulses of equal predetermined duration at the beginning and at the end of said amplified wave, the one of said square pulses at the beginning of said wave being in the negative sense and the one atthe end in the positive sense whereby said square pulse at the end of said wave is amplified by said second device.

DONALD E, NORGAARD.

REFERENCES CITED The following references are of record. in the file of this patent:

UNITED STATES PALENTS Number Name Date 2,266,154 Blumlein Dec. 16, 1941 2,217,957 Lewis Oct. 15, 1940 

